Cerebral Blood Flow using
pCASL MRI and Phase Contrast Angiography in a Large Cohort

Sudipto Dolui1, Raghav Mattay2, Ze
Wang3, Mack Finkel4, Alex Smith2,
Mark Elliott2, Lisa Desiderio2,
Ben Inglis5, Bryon Mueller6, Danny
J.J. Wang7, Lenore J. Launer8,
Robert Kramer8, R. Nick Bryan2,
and John A. Detre91Department of Neurology, University of
Pennsylvania, Philadelphia, Pennsylvania, United States,2Department
of Radiology, University of Pennsylvania, Philadelphia,
Pennsylvania, United States,3Department
of Psychiatry, University of Pennsylvania, Philadelphia,
Pennsylvania, United States,4Germantown
Friends School, Philadelphia, Pennsylvania, United
States,5Department
of Neuroscience, University of California, Berkeley,
California, United States,6Department
of Psychiatry, University of Minnesota, Minneapolis,
Minnesota, United States,7Department
of Neurology, University of California, Los Angeles,
California, United States,8Laboratory
of Epidemiology, Demography, and Biometry, National
Institute on Aging, Bethesda, Maryland, United States,9Departments
of Neurology and Radiology, University of Pennsylvania,
Philadelphia, Pennsylvania, United States

We compared whole brain cerebral blood flow (CBF)
measurements obtained using pCASL MRI and phase contrast
angiography (PCA) measurements in a large cohort of 544
subjects from the CARDIA study. CBF values showed highly
significant correlations throughout the velocity range,
providing no suggestion that pCASL labeling efficiency
drops at higher mean arterial velocities. There was also
considerable individual variability between CBF measured
by pCASL versus PCA, suggesting that PCA-based CBF
calibration of pCASL labeling efficiency may not be
justified at the single subject level.

Regional cerebrovascular reactivity (CVR) to CO2 is
increasingly measured with BOLD and ASL MRI. The data
processing is based on the assumption of a linear
relationship between BOLD/CBF and CO2. However, we show
that the BOLD CO2 reactivity curve has a sigmoidal
shape, but the CBF-CO2 relationship is linear in the CO2
range of 3 kPa to 8 kPa. These findings underline a
cautious approach to interpreting the CO2 CVR data
measured with BOLD and support the conclusion that CBF
is a more robust tool for CO2 CVR measurements.

16:54

0214.

Are blood flow measurements
by means of Transcranial Doppler valid under different
levels of end-tidal CO2? A high resolution MRI study at 7
Tesla of the middle cerebral artery diameter under hypo- and
hypercapnic conditions

Changes in blood flow velocity measured with
Transcranial Dopper (TCD) are frequently interpreted as
being proportional to cerebral blood flow assuming a
constant diameter of the insonated vessel. Reported data
on vessel diameter changes under influence of CO2 are
inconsistent. High resolution MR imaging was used to
measure the diameter of the middle cerebral artery (MCA)
in healthy volunteers. Four levels of end-tidal CO2 were
administered via a face mask. Results indicate that
moderate hypercapnia (+2 kPa above resting
concentration) increases MCA diameter 17%. A quadratic
model is proposed to correct for diameter changes under
different end-tidal CO2 conditions.

17:06

0215.

Quantification of CBF
Changes in the Human Brain During Moderate Exercise With
pCASL

In this study we investigate the effect of moderate
exercise on brain cerebral blood flow (CBF) using
arterial spin labeling (ASL) measurements. A dedicated
setup with an ergometer pedal platform in the
MR-BrainPET scanner was utilised. We demonstrated that
with this setup and by measuring with pseudo-continuous
arterial spin labeling (pCASL), the variations of CBF in
a healthy brain during exercise and following exercise
can be detected and evaluated.

A comprehensive investigation of peripheral
microvascular function in patients with peripheral
artery disease (PAD) is presented. The rate of recovery
following induced ischemia is monitored by dynamic
acquisition with Perfusion, Intravascular Venous Oxygen
saturation, and T2* (PIVOT). Analysis of the association
between the ankle-brachial index (ABI), which is the
clinical mainstay of PAD detection and diagnosis, and
PIVOT-derived time-course metrics found significant
correlations between ABI and time to peak perfusion and
between ABI and time to peak T2*.

High spatial and temporal resolution contrast enhanced
MRI is the cornerstone of detection and characterization
of focal liver lesions. An interleaved variable density
undersampling pattern with dual-echo bipolar readouts
and data-driven parallel imaging was modified to acquire
volumetric images of the liver every four seconds.
Parallel imaging calibration lines were only acquired
once during the breath-hold. Images acquired in ten
patients with focal nodular hyperplasia showed
significant improvement in overall quality compared to
clinical DCE images. MR angiograms were also obtained
from the arterial phase of the time-resolved series, and
were found to be comparable to the dedicated
conventional MRA.

DCE-MRI was performed to differentiate 4 spinal lesions
(9 myeloma, 22 metastatic cancer, 7 lymphoma, 22 benign
tuberculosis). The peak signal enhancement, the steepest
wash-in slope and wash-out slope were measured.
Two-compartmental pharmacokinetic model was used to
obtain Ktrans and kep, by using three different blood
curves (fast, medium, and slow). The results showed that
kep analyzed by using fast or medium blood curves is the
best parameter to differentiate these 4 lesion groups.
Ktrans is associated with wash-in slope and kep is
associated with wash-out slope. The slow blood curve is
not suitable for a short DCE period.

18:06

0220.

DCE-MRI before and after
induction chemotherapy in squamous cell carcinoma of the
head and neck

This study investigated the changes in DCE-MRI
parameters due to induction chemotherapy for head and
neck squamous cell carcinoma. In RECIST responders,
extravascular-extracellular volume was significantly
different before and after therapy whereas in
non-responders it was not. A third examination at the
end of therapy, long-term followup and histological
markers of hypoxia might reveal further correlations
with early imaging.

DCEMRI of the breast is a valuable tool in the detection
and staging of breast cancer. Radiologists rely on
measures of uptake and washout of contrast media by
analyzing the signal enhancement of suspicious lesions.
Signal enhancement can vary due to scanner and
acquisition parameters. Eleven volunteers were scanned
at both 1.5T and 3T to quantify the variability in
signal enhancement measures. We found that SER and time
to peak enhancement had the lowest variability.
Conversion from signal enhancement to concentration of
contrast media did not significantly reduce variability,
likely due to B1 inhomogeneity and uncertainty in native
T1 estimation.